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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

Go for it!

Triathletes will buy it as long as you give them some calculations "PowerCrank-style".

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

Similar things are used in motorsports to keep the fuel from sloshing around the tank and throwing the center of mass off and messing with your traction. So there's some precedent there, but mostly for cornering concerns, not front-back. If I remember correctly the ones I had seen used huge open-cell foam-ish material shoved into the tank to keep the liquids in place.

So yes, putting an insert would stop the fluid from moving around. But what advantage would that have? Good question.

Well... you might want to do some rigorous fluid dynamics modeling. It could be that enabling fluids to move freely is better than baffling the movement. Picture it this way... lets say you have a huge water bottle, and the water is free to move side-to-side. If you jerk the bike side to side, the fluid would stay in place relative to its original location (it would move relative to the bottle). In that scenario, no work is being done on the water, and jerking the bike back-and-forth takes less effort. However, if that water is bound to the bottle, and must move with the bike and bottle (it moves relative to original location, but not relative to the bottle), then you are doing work on the water, and using more energy.

I vote for no baffle.

I'm not sure this is a problem to begin with for mostly forward translation.. I understand the intuition that sloshing is bad, but that might not be the case. If you track the movement of the center of mass of the fluid in the bottle, it is moving forward and back in the bottle; to make it switch direction, the bottle is applying a force on it in oscillating directions. These should mostly cancel out (on first thought) so I don't think one would lose too much momentum/energy to this movement. Yes it takes energy to initiate this motion, but assuming there isn't much friction, it doesn't take much energy to keep that motion going. In fact, if you add friction to the system, it may actually result in the bottle being more parasitic than it would be otherwise.

In terms of stopping the sloshing motion, you're thinking about adding a damper to the system, which may indeed dampen out the oscillation if it is strong enough but that may not be necessary.

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I like analyzing things - http://engineeringfitness.org

I don't think the sloshing is taking a measurable amount of energy from what you are putting into the bike, averaged over more than a second or so. After it sloshes backwards, it will slosh forwards.

As mentioned, there is some control of fuel movement in race cars but this is for maintaining balance for cornering. The amount of water in your bottle is not a concern for this.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

Some of the handlebar drink systems have this in a form already. The mesh thing that the PD bottle had for instance.

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Developing aero, fit and other fun stuff at Red is Faster

Hello stumpyx13 and All,

While it would slow you down a bit .... you could harness that slosh to power your Garmin.

https://www.cbsnews.com/...kes-us-debut-hawaii/

Solar collection on hat and shirt back would be more efficient and not slow you down and maybe keep you cooler.

http://www.dailymail.co.uk/...charge-phone-go.html

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Cheers, Neal

+1 mph Faster

That is/was to keep liquids from sloshing out of the bottle.

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

Yes! a little impeller in there connected to an alternator! You'd never need to change batteries in your power meter again!

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

Use it to power the motor in your seat tube.

This is a big problem in liquid fuelled rockets actually and these baffles are installed inside the fuel tanks to prevent sloshing. So go for it. Make these. Market them as rocket-o-matic speed-o-whamo and triathletes will pay $50 a pop just for these baffles easy. We'll buy anything. It doesn't matter if it works or not.

But think of the marginal gains! The way one could actually justify it (?) is that the forward slosh doesn't return quite all of the energy... some will be lost to turbulent (viscous) friction. What we need is a bottle or hydration system with hydrophobic inner surface so you're guaranteed to get all the water.

Vaguely relevant note: I did build a couple of cars using Fuel-Safe cells. The foam definitely works. But any significant methanol content turns it to crap.

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Less is more.

Formula 1 and rocket science endorsement sounds good!



While the forces and volumes for cycling are smaller we also don't have 1000hp engine so any energy saved is better.

Without science it's hard to estimate the energy savings. I can't imagine fluid pushing to the back of the bottle and staying there. Is it like a poster said that the water is relatively at constant speed and the bike is moving around it? I know energy isn't created or destroyed so when water moves back and forth that energy has to come from somewhere....guessing absorbing momentum from the biker. That force might be small or it might not....if you hold a filled bottle and just oscillate it slowly back and forth for an hour it definately feels like work and costs energy

The idea of the 3d hashtag over a sponge shape is so that bottle volume, drinking and filling speed aren't compromised

There might have to be some horizontal fins to prevent vertical sloshing inside the compartment

To test this theory could measure water bottle versus frozen water bottle on a model to see what the fluid inertia costs are?

As you and others have mentioned, it shouldn't be too hard for someone with the requisite skills to model. I'd be surprised if it's a significant amount, even if you're crit racing with lots of cornering and accelerations.

Also, with respect to motorsport, one of the key reasons for fuel tank/oil sump baffles is to make sure that during periods of sustained sideways g-force (e.g. long corners) that all the fuel/oil doesn't slosh to one side of the tank, away from the feed pipe and starve the engine of fuel/oil. Obviously this isn't a concern in water bottles.

Can't wait for the double priced Carbon version of the basic plastic one! Saving me 0,001g!

You stop there with a baffle. Why not develop a KERS kinetic energy recovery system like formula 1 cars. Imagine the energy you could save with up top three sloshing water bottles on a bike that could be used later on hills or the overtake when pulling out the draft zone...

https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system

I thought the OP was joking. Now, not so sure.

If there are energy losses from the water sloshing, then the baffle will increase the amount of energy dissipated (that's what baffles do) and make you slower. In theory anyway.

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

I thought the intention would be from preventing fluid accelerating and moving - thereby avoiding some dissipation?

An aero bottle already would reduce the distance fluid can slosh sideways, but increases the distance water can gain momentum in the other direction

If you have a BTA setup - and you brake - is there is a half kilo of water that shoots forwards - which could potentially affect handling - would baffles prevent acceleration or only spread out the dissapation across the chambers and end up with the same net forward force?

From a handling perspective possibly a difference in limiting sloshing.

From an energy perspective, it's all internal to "the system" and any energy imparted to slosh the water backwards pushed off the bottle in the forward direction in an equal but opposite manner negating the effect. The system in this case is you and your bike. From a handling perspective the mass movement is unpredictable, so the timing causes it to be an issue. From an energy perspective it will equalize over the oscillation of fluid movement. And the energy required to clean extra crap would negate any handling advantage.

It seems to me that any losses due to water movement in the bottle are going to come from shear resulting from the flow. So, there'll be some kinetic energy lost as heat due to liquid movement. It's not going to be very large IMO and it'll be rather difficult to estimate. Flows in an agitated bottle are going to be highly turbulent and entirely dependent on liquid properties, bottle size, shape and surface, bottle orientation and location on the bike, and exact motion of the bike. When your cadence changes, the frequency of the motion will change. When power or your position or the gradient, or wind changes, the amplitude and orientation of motion will change. As the volume of water in the bottle changes, everything changes. Far too many variables and any solution would be based on a myriad of questionable assumptions, making it worthless. The problem is an absurd one for which to attempt to produce a figure by calculation.

Now, if you put in a baffle, you can reduce the range of motion of the fluid. But how will that reduce energy loss?
In order for a baffle to prevent motion it must produce resistance. You can change the size, location and orientation of flows within the body of liquid, but you can't eliminate liquid movement. The same volume of liquid will remain in motion. What makes you think the baffle will reduce the losses due to that movement?
It's not a very intuitive problem! It's not immediately obvious whether a baffle will increase or reduce energy loss, but I'm pretty sure it'll increase it: see below.

You've described your proposal as a "wave breaker". Waves move potential and kinetic energy about incredibly effectively. To "break" the wave you would be introducing turbulence to mix the flow and damp the wave. Therefore wouldn't the breaker actually be the means of converting the energy from a useful form into heat more effectively than a simple bottle would ever achieve? And that's the opposite of what you want.

If it helps, consider a fluid trainer. The resistance is not created by moving a wave around. It is created by generating turbulence, i.e. lots of fluid shear in the resistance unit, and this creates heat which is dissipated into the ambient air through the body of the resistance unit. A bottle with baffles would do essentially the same thing by creating small scale turbulence that effectively converts kinetic energy to heat. I believe it would make things considerably WORSE not better than a standard bottle.

As others have pointed out, the comparisons made in some posts to rocket and motor vehicle fuel tank baffles are missing the point. Those are used to control the liquid to allow reliable access and to maintain control and stability. It's not about efficiency.

Yep, this^^^^^

I started writing my last post, went away for a while, came back and posted it only to find three other posts had appeared in the mean time addressing exactly the same points.

Do bottom line is ... Fluid moving in a space won't dissapate more than the same volume of fluid spread across 5 small compartments

I thought that the overall energy would be less when not giving the fluid enough space to create waves but can see that this energy would just be spread not reduced

Would've been great if waveless bottles made your bike feel less sluggish

Kind of on the same principle as compression clothing reducing muscle rebound in sprinting....

If the bottle is moving the same motion is being imparted to the fluid regardless. The movement of the liquid in the bottle in response to that motion is actually the very thing it sounds like you are trying to achieve - the water is "trying" NOT to accelerate. So if we just look at the longitudinal axis for simplicity and take a bike that is surging and slowing between pedal strokes: As the bike surges forward, the water tends to maintain it's existing velocity and accumulates at the end of the bottle closest to the back of the bike. The water is sloshing relative to the bike but it would be more useful perhaps to consider the bike agitating the water. It is reduction of the accelerations imparted by the bike that best allow you reduce energy loses. So ideally perhaps you would isolate the bottle from bike accelerations by allowing the bottle to continue moving at a mean rate as the bike surges and sways around it. But I doubt you can come up with a practical and worthwhile way to do that!

Interesting explanation!

So then a suspended BTA bottle setup could save energy by allowing the bottle to float independantly ...like neoprene hammock or springs instead of tiewraps ?

#notcarbon
#notgoingtoselltorichagegrouperwithtoomuchmoney

In theory, yes. But, in practice such a suspension system would need to be damped to prevent harmonic oscillations from being imparted to the suspended bottle---that dampening will just be absorbing energy, again. It would also need to be "loosely sprung", with a large range of motion to allow the bike to move without imparting too much force to the bottle. I think that's probably a loosing battle.

Personally I think that this is a really interesting idea.

There is little doubt that a conventional bike water bottle has a lot more fluid movement than a fully baffled bottle. And even more so when the bottle is not 100% full (which is most of the time). When the fluid sloshes back and forth, it does indeed 'steal' energy. An easy demo of this is a classic egg trick. When put on a smooth flat table, a raw egg is very difficult to spin and, once spun up, it slows down very very quickly. Not so with a hard boiled egg of exactly the same mass, it will spin easily and for a long time.

Heck, you can also really see this on a bike with a vertical aerobar bottle. Without a baffle, the liquid in any of the bottle designs sloshes like CRAZY. But, add a splash-reducing sponge, and you don't even need a lid on the bottle, the sloshing is reduced easy by 95% plus.

But, of course, the devil is in the details. How much energy does a couple of unbaffled water bottles on a bike really suck up?

If the energy loss is non-trivial (and, admittedly, that is a big 'if'), I think one would have to use a full foam insert in the bottles (vs just plastic baffle louvers as pictured above) to really reduce fluid sloshing significantly. Or at least that is my armchair quarterback opinion ... :^)

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
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Exactly. It's not a practical proposal. A simple spring won't cut it and as Tom says, the range of motion needed is significant. We're not talking 5mm of give in the bottle cage. More like an articulated cradle. It ain't a runner!

That's pretty poor example. The material properties of raw egg white are hardly the same as cooked. The cooked egg white has become bonded molecularly (ok, entangled might be a better term). But, the material is no longer fluid, and energy can be directly transferred from molecule to molecule...much more like a crystalline structure.

In the baffled case every little compartment is still filled with FLUID, which still moves in a loosely coupled manner. But, as Ai_1 points out...the sloshing itself is not the enemy. Its the halting of the sloshing via friction (internal sheer, and with the walls of the container/baffles). I'm sure there is a calculus to it, though. As you describe, if I subdivide the fluid fine enough (using open celled foam?), perhaps I get ahead of the game and less energy is imparted into the fluid in the first place.

But, those dividers take up space, and have mass of their own. How far to do I have to subdivide to start making ground on the energy loss? And how much mass/volume do the dividers take up, such that now I have to make my bottle larger in order to hold the same amount of fluid? At which point, now I may be trading aero energy loss.

If I were going to even consider pursuing this, I think I'd do some testing to find out how much actual energy loss we're talking about. Two bottles equal mass, one filled with water, one filled with solid resin or something. Dunno if Chunging would be sensitive enough, but it'd be worth a shot. If not, that's probably an answer right there.

In the realm of tri products that provide marginal (or better yet unproven) gains at an exorbitant cost, baffles in a water bottle sound great. Ceramic Speed Works sells their OSPW system for about $500. You save 1 watt/$250. If this baffle might save 0.2 watts, $20 is perfectly reasonable for people to take a flyer on. It might work or it might not, but for $20, they can try it themselves.

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Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour

Of course, I fully understand that a cooked egg is not the same as a raw egg. I was just using that as an general example because, the smaller and smaller the baffles, the closer to an effective solid the liquid water will become (only an approximation, of course). I don't know how much one would have to subdivide a water bottle to get 95% of more of the liquid to stay stationary, but I imagine that it would be a lot, that is why I mention using foam as baffling vs just using a few plastic louvers.

But I can say that, watching a vertical aerobar water bottle both with an internal foam baffle and then the same bottle with nothing, the visual difference between the two is enormous in terms of liquid movement.

Is the energy savings very much? Who knows?
But that is for testing to decide.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
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As long as we're in this weird twilight zone of not knowing how serious OP is, how about bottles with internal bladders?

And you could even build something like that directly into the frame of a bike...certainly no one's thought of that!

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Eliot
blog thing - strava thing

I think a simple test will (dis)prove this rather rapidly. Take 2 identical bottles. Fill them both with the same amount of water. Freeze one.
test 1: ride w/ the bottle full of liquid
test 2: ride w/ the bottle full of ice.

I can save you the hassle. There's not a difference large enough to even discuss here. However, as so many have pointed out, still may be worth making and selling as people will buy anything. Please check my site below and buy a few hologram bracelets from me. They have really improved my racing this year!

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http://triathletelife.wordpress.com/

Find the marketers of Halo they would be all over this...

making fluid sway inside 2 or 3 bottles with fluid swaying constantly for 5 hours cant be nothing


the baffles would also have to work vertically so there might need to be fins like this - to create smaller compartments but that still dont block flow for emptying or filling and also dont take up space inside the bottle like a sponge...

that reminds me of the elastic drink bladder with bite valve from the 90s - called the airstream or jest stream or something .... youre right in that an elastic capsule like that could contain wave formation



edited to add.... it was called bikestream

It is essentially nothing bc your linear accelerations are so slight across that time that the forward and backward movement of the water has nearly no effect on your inertia. But like I said, the test is really simple. The frozen water is effectively perfectly baffled. You’d be much better off to just get some lighter shoestrings or cut some of the unused Velcro off your shoes. Seriously.

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http://triathletelife.wordpress.com/

Its not, but it might be damn near. let me ask it this way:

if we insulated your water bottle with a giant vacuum flask so that no heat could enter the bottle or escape from it, then all that heat would have to warm up the liquid inside the bottle. How much do you think 32oz liquid would heat up after 1 hour of sloshing on the bike? 1 degree, 10 degrees, 50 degrees?



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A little physics:

32oz = 896 grams (or CCs)
It takes 1 Calorie per gram to raise the temperature of water 1 degree C.
1 watt = 0.24 Cal per second
3600 sec = 1hour

So, it takes 896 calories to raise the temperature of that bottle by 1 degC. Lets say that happens in an hour. 896 cal / 3600 sec = 0.2489 cal/sec or roughly 1 watt.

Therefore, if the water is absorbing 1 watt continuously for an hour it should be 1 degC (or 1.8 F) warmer after an hour (assuming it is well insulated). Does that seem reasonable? Maybe...hard to say really.

That's kinda convenient, because it makes other cases pretty simple to consider. 10 watts would mean it would be 10C or 18F warmer. I think that's clearly preposterous. Even if I put a water bottle on a paint shaker for an hour, I'd be SHOCKED if it was almost 20 degrees warmer afterwards (70F => 90F). I shouldn't even need insulation to detect this amount of heating.

My guess is that it is somewhere well below 1 watt.

not a lot of acceleration/deceleration in long course tri, which would seem to be the primary targeted use for this.
maybe send it over to team cambell soup rebels.

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http://www.PatGriskusTri.com USAT Certified Race Director
2024 Races: USAT State of CT Age Group Championship/State of CT HS Champs/ CT Club Championship - Sat June 15th (Oly/Du/Sprint) Hopkins Vineyard Tri at Lake Waramaug Saturday July 13th http://www.HopkinsVineyardTri.com

I bet the Ventum reservoir could benefit from fuel cell like foam..... However I bet for my long runs I would be more likely to carry a bottle if it did not bounce around as much. Perhaps the better application is for runners....

The ventum resevoir might benefit in terms of eliminating any off putting harmonics but it's questionable if it would otherwise impact performance.

With running the forces are in more oscillating directions.... I can imagine that baffled water might make the bottle bounce more. With biking force being in a constant direction the thought was keeping water going in the same direction too somehow.

For running I imagine a vest with 4 compartments could help...like a camelback but spread left/right and front/back with a communicating tube at top ... So that forces are only applied to a small segment of water at a time during each phase of running step

Example...you would have quarter of the fluid on the side of the leg during footstrike

Do motorbike tanks have baffles?

When I've tried carrying a bottle on a belt, for example, it was the weight I noticed, not the sloshing. i.e. it was most annoying and noticeable when the bottle is completely full (no sloshing if its full). if the bottle was half full it bounced far less, even though the liquid inside sloshed around a lot more.

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

Baffles serve a purpose - control of liquid movement. I don't contest that.
It's useful/necessary for many reasons and would probably be helpful in running hydration applications. But there are 3 different topics being continually mixed together throughout this thread and it's not useful.

1. Trying to use fluid motion reduction within a vessel to reduce energy loses
2. Control of liquid movement to maintain proximity to pick up tube for vehicle fuel or hydration purposes
3. Control of liquid movement to control mass distribution changes for dealing with handling, harmonics and comfort issues

It seems to me that you're thinking about a solution and looking for corresponding problems. That's not generally a useful approach unless you have a product and you're trying to figure out a way to sell it. From an engineering approach, you typically start with a problem and look for a solution.
Regardless, I'd suggest disentangling the potential problems you want to address. Whether a baffle is used in a motorbike is not useful in deciding whether you want one on your bike unless you know WHY it is or is not on the motorbike.

I see zero point in talking about fuel tanks on motorbikes if you want to know about bicycle drink containers:

• Large volume of fuel stored high up on a motorbike, thus might be potential dangerous handling issues - not an issue for a bicycle
• Tank rigidly attached to the vehicle and needs to provide a constant flow of fuel - not applicable on a bicycle: you hold the bottle in your hand to drink or in the case of a BTA bottle, you use it while velocity is pretty constant.

May I ask - What specifically is the purpose of this topic at this point? I'm getting lost.

Thanks...

The idea
marginal gains through controlling excess fluid movement inside water bottles on the bike

Purpose
reduce incidental fluid accelerations and momentum caused by fluid (in some cases 1 and half kilo worth) rocking in all directions but forward - that could detract from the bikes overall forward momentum

Potential Result
- conserving forward momentum when biking
- making the bike feel less sluggish - there is no rebound time for the water vector to move forward again - like compression clothes preventing muscle rebound
- better handling during braking and steering (in the case of a half kilo or more of water sloshing forward on a horizontal BTA system or horizontal frame reservoir)

The question was
If it made sense
How much could be saved

There have been some great answers! thanks to all

You should probably go back to basic physics to prove that water movement inside a bottle is actually a bad thing. You may find (I think you will find) that it is actually a good thing from the perspective of conservation of energy. You are focused on movement of the water relative to the bottle & bike. You should be thinking about movement of the water relative to the earth. The less it is baffled, the less it moves relative to earth. The less the water moves relative to earth, the less energy is needed to move the system as a whole.

Second, you should probably reconsider the order of magnitude. A full bottle would have very little of this movement, with or without a baffle. So, a typical BTA or frame bottle with 700g of water would have very little movement when full. Conversely, a nearly empty bottle (say ¼ full), would have ample room for movement, but the mass would be 175g. Therefore, your concern over potentially “1 and a half kilo” should probably be reduced by an order of magnitude.

Create a test rig that compares the energy required to oscillate a bottle at ~3Hz. Then, test a 1/2-filled bottle with frozen water (perfect baffle) and thawed water (normal). You could try it at different volumes just to compare how volume factors in the measurements.

This sounds like a great analysis aswell

So if true....does a aero bottle act like a baffle compared to a round BTA with space for fluid to float?